Géraldine DOURY

Doctor in Life Sciences, Associate professor
Speciality: Ecophysiology of interactions between host insects and entomophagous insects
Team: BIPE
geraldine.doury@u-picardie.fr

Research interests

Host-parasitoid interaction is based on heterospecific parasitic interactions between two arthropods often belonging to the same class, that of Insects. A major constraint for the parasitoid is the achievement of growth and development at the expense of its host, which it facilitates by the introduction of various factors into the host, subsequently manipulating its physiology. In particular, the challenge for an endoparasitoid is avoidance of the immune defense reactions induced by a host following infestation, and directed against the parasite developing in its hemolymph. As part of my research post PhD I am developing an understanding of the mechanisms governing the outcome of the parasitic relationship, in each of the two interacting partners. The objectives are twofold:

•  To search for physiological and cellular targets of the parasitoid in the host and to identify factors and molecular mechanisms that determine successful parasitism,
•  To study the role of cellular immunity effectors  leading to the defeat of the parasite by its host, and the effect of various factors on their efficiency.

Since my recruitment as a lecturer, my research within the BIPE team has been focused mainly on the host-parasitoid model of our laboratory, comprising various species of Drosophila fruit fly hosts and their braconid parasitic wasps of the Asobara genus. My work aids in highlighting the variability of virulence mechanisms used by parasitoids of the Asobara genus, and to distinguish them from other Braconidae parasitoids. In recent years I have also taken part in studies involving other biological models, namely aphid parasitoids.

Key words

Insects, sustainable interactions, host-parasitoid systems, Drosophila, Asobara, resistance, virulence, venom glands, ovarian fluids, cellular immunity.

Recent projects

Effects of parasitoids on their hosts
In the Evparasitoid (2005-2008) and Paratoxose (2009-2012) projects supported by the French ANR  I participated in the analysis of factors injected by female parasitoids of the Asobara genus into Drosophila host larvae. Study of their effects on the physiology and outcome of post-embryonic development of hosts have shown that the venoms synthesized by females are responsible for the induction of transient or permanent host paralysis depending on the wasp species. These effects are also found during in vitro injections of venom extracts into host larvae. Interestingly, ovarian extracts from Asobara japonica can act in an antidote manner to reverse the effects of venom. Indeed females use both venom and ovarian secretions to regulate the host physiology for the successful development of their progeny. I tested the fractions obtained after FPLC separation of ovarian or venomous extracts from A.  japonica females for their effects on the microinjected host larvae, the aim being to identify the active molecules responsible for the deleterious effects measured on the survival and development of Drosophila melanogaster larvae when parasitized. The identification of molecules involved is currently undertaken by Marianne Jaubert as part of her Post-Doctoral fellowship in the laboratory.

Host response to parasitism and cellular immunity
The resistance of fruit fly host species to parasitoids also varies. Larvae of Drosophila subobscura are unable to build capsules even against avirulent parasitoids, because of their innate deficiency of one category of hemocyte, the lamellocyte. The unexpected discovery of such an immunodeficiency in natural populations of insects led us to screen the various species of the obscura group for the presence / absence of this character and then to investigate the causes. This work, carried out as part of the PhD thesis of Sébastien Havard (2005-2009) which I co-supervised also characterized both morphologically and functionally, atypical hemocytes produced by certain species of this group of flies.

Effects of temperature on host-parasitoid interactions
In the Climevol (2009-2012) ANR project I also work on the effects of temperature on the Asobara tabida / Drosophila interaction. The effects of moderate heat stress on life span and  parasitic success of the aphid parasitoid Aphidius ervi (Aphidiidae) was studied by Ibrahim Ismaeil during his PhD, which I co-supervised. The work on aphid parasitoids clearly demonstrates the existence of trans-generational phenotypic plasticity, and suggests that adaptation to thermal stress can be achieved via maternal effects. It also illustrates the complexity of insect responses and underlying mechanisms to the changing conditions of their natural environment.

Teaching

Cell Biology, Developmental Genetics, Zoology, Immunology, Reproduction in animals.

Directions or joint management of thesis

2005-2009 Sébastien HAVARD, « Defense potential and cell encapsulation in Drosophila of the obscura group ». Co-supervision (33%) with P. Eslin (Lecturer, BIPE) and G. Prevost (Pr, BIPE)
2007-2011 Ibrahim ISMAEIL, « Effets d’un stress thermique chaud sur les traits de vie et le succès parasitaire du parasitoïde de pucerons Aphidius ervi(Aphidiidae), agent de lutte biologique ». Co-encadrement (33%) avec A. Couty (Lecturer, BIPE) et G. Prévost (Pr, BIPE).

Current administratives tasks

Member of several selection committees (section 67) for the recruitment of temporary and permanent Lecturers, in both my home and external organizations.
Review of articles for European Journal of Entomology and Functional Ecology.
Elected member of the Unity Council of Edysan.
Correspondant for the scientific animation of the unit.

Recent publications

ESLIN P., PREVOST G., HAVARD S. and DOURY G. (2009). Immune resistance of Drosophila hosts against Asobara parasitoids: cellular aspects. In Parasitoids of Drosophila, Advances in Parasitology, Vol. 70, Burlington: Academic Press, pp.189-215.
HAVARD S., ESLIN P., PREVOST G. and DOURY G. (2009). Encapsulation ability: are all Drosophila species equally armed? An investigation in the obscura group. Canadian Journal of Zoology, 87: 635-641.
MOUNDOUNGOU-MABIALA A.D.N., DOURY G., ESLIN P, CHERQUI A. and PREVOST G. (2010) Deadly venom of Asobara japonica parasitoid needs ovarian antidote to regulate host physiology. Journal of Insect Physiology, 56 (1): 35-41.
PREVOST G, ESLIN P., CHERQUI A., MOREAU S. and DOURY G. (2011) When parasitoids lack polydnaviruses, can venoms subdue the hosts ? The study case of Asobara species. In Parasitoid Viruses: Symbionts and Pathogens. N.E. Beckage and J.M. Drezen (Eds). Elsevier, pp. 255-266.
HAVARD S., DOURY G., RAVALLEC M., BREHELIN M., PREVOST G. and ESLIN P. (2012) Structural and functional characterization of pseudopodocyte, a shaggy immune cell produced by two Drosophila species of the obscura group. Developmental and Comparative Immunology, 36: 323–331.